Two Faces of Mars (from the Moon)

Moon-facing hemisphere of Mars on 8 May 2014 at 14:27:04 UTC seen from lunar orbit! Instruments on LRO sometimes use stars and planets for calibration or other special observations. During one of these off-Moon observations, LROC imaged Mars. This Moon-facing hemisphere of Mars has a dark (low albedo) feature on the west limb (left) that is Acidalia Planitia, and the bright (high albedo) region on the east limb (right) is Arabia Terra. LROC NAC M1154198455R is enlarged by a factor of 7 [NASA/GSFC/Arizona State University].

During off-Moon observations on 8 May 2014, LROC captured two images of Mars!

Two images of Mars acquired about four hours apart. The earlier image includes a view of Syrtis Major (dark splotch on center right of Mars shown in left image); the later image includes a view of Acidalia Planitia (dark splotch on upper left of Mars shown in right image). LROC NACs M1154184252R (left) and M1154198455R (right) upscaled by a factor of four [NASA/GSFC/Arizona State University].

Mars is approximately 10 pixels across in the two NAC images. The size of Mars in the NAC cameras is a function of the Moon-Mars distance, which on 8 May 2014 was about 100 million km. When Mars is at its minimum distance (55 million km), it fills about 14 pixels in the NAC, and when Mars is at its maximum distance (400 million km), it is less than two pixels wide.

These two images were acquired about four hours apart; during this period, Mars rotated roughly 60º degrees in longitude. Both Earth and Mars have similar rotation rates of roughly 15º of longitude per hour. Planetary rotation allows views of different regions of Mars over time. With only ten pixels, however, it is difficult to make out specific martian surface features.

The dark splotch on the center right of the eariler Mars image is Syrtis Major Planum. The dark splotch on the upper left of the later image is Acidalia Planitia, a large lowland basin in the northern hemisphere of Mars. The brighter area in both images is Arabia Terra, a large highlands region also in the northern hemisphere.

Mars features were identified using the MarsWatch tool, and distances were calculated using the SPICE GUI tool.

See more examples of LROC calibration imaging and engineering targets: